BUILDING STONE. , 629 
The strata suitable for building purposes are from 1 foot to 10 feet in 
thickness, and the material which does not make an excellent quicklime 
is comparatively small. As a building stone the material is superior to 
much of that used in counties to the southwest, although not equal to the 
Sandusky and Marblehead limestones. It is ofa light drab color, full 
of small cavities, and works very easily, and some of it is soft and pure 
enough to be sawed. ‘The stripping is sold for macadamizing. It pre- 
sents the usual microscopic characteristics of the Helderberg rocks, and 
it dissolves in hot acid, leaving a very slight residue. The qualitative 
analysis indicates that it is composed of remarkably pure dolomite. 
CoRNIFEROUS.—Quite a variety of stone is found in the neighbor- 
hood of Columbus, for although Franklin county is flat it has a number 
of geological formations within its limits. To the east lie the Waverly 
sandstones and the Huron shale, but the limestones of the Corniferous, 
which lie to the west of Columbus, are by far the most important from 
an economic stand-point. Thick and heavy layers of stone exist among 
the strata. From the different layers material suitable for the most 
diverse uses can be obtained, good quicklime can be made, and being in 
part a very pure carbonate of lime, the stone is desirable as a flux for 
smelting iron ores. Of late it has been very extensively applied to the 
latter purpose, especially in the Hocking Valley region. The quarries are 
all situated a few miles to the west of Columbus, and have been operated 
for a long time. Some which have been the most important, for instance 
the state quarries, from which the material for the state-house and for 
walls of the state-prison was extracted, are no longer worked, but all of 
the quarries mentioned in the census tables are immediately about the old 
quarries and extract the same material. While the state-house was in pro- 
cess of construction, and stone of the best quality was in demand, the Cor- 
niferous limestone was worked to a greater depth than it is at present, for 
the finest quality of stone is found in the lower layers. At present the 
production of building stone is subordinate to the production of lime 
and flux. 
The Columbus limestone is dense, compact, and strong. There are 
12 feet of the upper courses in the present quarries that average 93 per 
cent. of carbonate of lime, and frequently the percentage rises to 95 or 
96, while, on the other hand, there are localities where the Corniferous 
limestone becomes nearly a typical dolomite, as at Bellefontaine. The 
stone is fossiliferous, but the fossils are very firmly cemented and do 
